The present invention relates to electromagnetically actuated valves and more particularly to such valves of the disc type.
In a gasoline engine, the standard fuel injector port in the air manifold has a diameter of 14 mm. Disc-type gasoline fuel injectors are known and typically involve a double working pole magnetic circuit. In order to house the structures forming the magnetic circuit and the fuel path of the conventional disc-type injector, the main body portion of the disc-type injector requires a relatively large diameter and cannot be inserted into the standard port. This limits the ability of engine designers in their designs of the air manifold and air inlet. A disc-type gasoline fuel injector is disclosed in U.S. Pat. No. 4,917,307 to Baxter et al. A hollow generally cylindrical outer body 11 formed of magnetic material surrounds a hollow flanged core member 13, also formed of magnetic material. A former 16 made of synthetic resin material surrounds core 13, and a solenoid winding 17 is wound around former 16. Body 11 defines an integral radially inwardly extending annular shoulder 18. An annulus 19 is trapped against annular shoulder 18 by means of a non-magnetic valve seat member 21, which itself is held in position by means of a tubular outlet member 15 which projects into the air inlet manifold of the gasoline engine. Seat member 21 is configured in the form of a disc, the diameter of which is equal to the internal diameter of body 11. Seat member 21 has a central orifice 22, which is surrounded by an inner annular seat element 23. A plate valve member 24 is biased by a spring 26 into contact with inner annular seat element 23, which is disposed within annulus 19. The valve is checked for flow while the tension in spring 26 against valve member 24 is set by staking the calibration slide into the position that yields the desired flow. Then the filter is inserted into the inlet 12 of the body 11. Valve member 24 has a plurality of openings 25 and is formed of magnetic material so that when winding 17 is energized, the flange 18 and core member 13 assume opposite magnetic polarity. The valve member 24 is attracted away from the seat element 21 against the biasing action of the spring 26 so that fuel can flow through the passage 14 and openings 25 to the central orifice 22. Movement of the valve member 24 towards the annular shoulder 18 is limited by a non-magnetic shim (not shown).
In valves of this type, critical dimensions such as the air gap typically are set during manufacture by grading shims or the thickness of other components. For example, non-magnetic plates may be inserted on one or both of a moving magnetic pole and a stationary magnetic pole.
One attempt at providing a fuel injector of very small size and very simple structure that can be produced at low cost is disclosed in published European patent application publication number 0 536 774 A1 to Babitzka et al. In this bucket-type injector, the body 1 houses an annular electromagnet 2 in which a tubular core 3 is disposed. The shutter member 4 is fixed to an armature 6 that can be magnetically attracted to the tubular core. The injection orifice 5 is formed in an element 8 that is configured with a flat bottom wall that is laser welded to the lower section of an annular wall 7, which is configured with two concentric sections of different diameters. The lower section 9 of the annular wall 7 has a relatively smaller diameter than an upper section 10 of the annular wall 7. A sealing ring 13 and a spacer washer 14 are disposed between the tubular core 3 and the upper section 10 of the annular wall of the annular ferromagnetic element 7 that partially houses the lower end of the core and partially houses the sealing ring. A tubular casing 15 formed of sheet metal contains the annular ferromagnetic element 7 and the tubular core, and the lower end of the casing 15 overlies at least a part of the annular wall 10 of the annular ferromagnetic element 7 and is fixed to the annular wall 10 of the annular ferromagnetic element 7 by means of a laser weld 19. A further laser weld 21 attaches the opposite end of the casing 15 to a flange 20 formed in the opposite end of the core. A magnetic circuit with a single working-pole is formed within the core 3, the armature 6, and the wall 10 of the ferromagnetic element 7. However, bucket-type injectors, while typically having a magnetic circuit with a single working-pole, are noisier and more prone to leakage than disc-type injectors.